Petroleum distillate fuel oils are susceptible to deterioration during storage or use. Discoloration and insoluble sludge, gum and sediment often result, making the fuel less acceptable to the customer since it is more apt to clog screens, filters, nozzles, etc., of equipment in which it is consumed. Resistance to discoloration and the accompanying formation of insolubles is, therefore, a desirable property of present day fuel oils, such as heating oils, diesel fuels and other hydrocarbon distillate fuels. Storage stability of distillate fuel oils is usually determined by accelerated tests which are carried out under oxidative conditions at elevated temperatures.
In the past, several types of additives, including a large number of different amines, have been reported as stabilizers for distillate fuel oils and other similar petroleum products. Chao et al., in U.S. Pat. No. 4,264,461 disclose stabilized hydrocracked lubricating oils containing aliphatic amines having the structure: ##STR1## wherein R, R.sup.1, R.sup.3, and R.sup.4 may be hydrocarbon; R.sup.2 may be divalent hydrocarbon, and x and y are 0 to 10. Only a single aliphatic diamine is found among the specific compounds disclosed by Chao, viz. N-alkyl-1,3-propylene diamine (alkyl group derived from coconut oil fatty acids); all others are monoamines. Andress, in U.S. Pat. No. 2,945,749, discloses certain tertiary alkyl primary amines as stabilizers against color development and insolubles formation in fuel oils during storage. On the other hand, Bonner, in U.S. Pat. No. 2,672,408,and Alink et al., in U.S. Pat. No. 4,040,799, disclose secondary and tertiary amines as being effective in stabilizing fuels oils. Dunworth, in U.S. Pat. No. 3,490,882, and Braxton, Jr., in U.S. Pat. No. 4,509,952, disclose the use of tertiary amines for stabilizing distillate fuel oils.